@article {63, title = {Nitrogen budget of Lago Maggiore: the relative importance of atmospheric deposition and catchment sources}, journal = {J. Limnol.}, volume = {60}, year = {2001}, pages = {27-40}, abstract = {Hydrological and chemical data of 1996 and 1997 are used to evaluate the relative contributions of atmospheric deposition and urban/industrial wastewaters to the nitrogen budget of Lago Maggiore. The atmospheric load of nitrogen was about 80\% of the total input to the lake, with negligible variations in dry (1997) and wet (1996) years. A comparison of the two study years with the yearly N budgets evaluated from 1978 to 1998, showed that the N load was higher with increasing amounts of precipitation/water inflow. Soils and vegetation act as N sinks; the \% retention varies between 40-60\% for the forested catchments with low population density in the central-northern part of the basin, to values close to zero or even negative in the south, indicating a net leaching from the soils. The Traaen \& Stoddard (1995) approach revealed that all the catchments of the major inflowing rivers were oversaturated with nitrogen. The long-term trend of nitrogen concentrations in Lago Maggiore (1955-99) is analogous to the trend for atmospheric deposition (1975-99), which is related to emissions of nitrogen oxides and ammonia in the atmosphere. The relationships between the present N load and in-lake concentrations are discussed using a budget model, which is also used to infer the pristine load of N. The close relationships between N trends in lakes Maggiore, Como and Iseo, and the geographical and anthropogenic features common to their catchments, suggest that the results obtained for Lago Maggiore can be extended to a wider area.}, keywords = {atmospheric deposition, catchment, Lago Maggiore, nitrogen budget, river water}, author = {Mosello, R. , Calderoni A. , Marchetto A. , Brizzio M. C. , Rogora M. , Passera S. , Tartari. G. A.} }